Making a plastic household item on a home 3D printer is greener than making them en masse in a factory and shipping them to a warehouse, a U.S. study found.

While common sense might suggest mass-producing plastic widgets would take less energy per unit than making them one at a time on a 3D printer, Michigan Technological University researcher Joshua Pearce reports that's not the case.

Pearce, a professor of materials science, and his colleagues conducted life cycle impact analyses on three products: an orange juicer, a children's building block and a waterspout, tracking energy use from raw material extraction to one of two endpoints: entry into the United States for an item manufactured overseas or printing it at home on a 3D printer.

Making items on a basic 3D printer took from 41 percent to 64 percent less energy than making them in a factory and shipping them to the United States, Pearce's study found.

Home 3D printers, about the size of microwave ovens, work by melting filament, usually plastic, and depositing it layer by layer in a specific pattern.

"The bottom line is, we can get substantial reductions in energy and CO2 emissions from making things at home," Pearce said. "And the home manufacturer would be motivated to do the right thing and use less energy, because it costs so much less to make things on a 3D printer than to buy them off the shelf or on the Internet."